Lapping method and machine



Sept. 24,1946. I D. s. OLIVER 2 8 4.

LAPPING METHOD AND MACHINE v Filed July 31, 1944 2 Sheets-Sheet 1 2119'.j a] E Zea/Z672! liver D. S. OLIVER LAPPING METHOD AND MACHINE Sept. 24,1946.

Filed July 31, 1944 2 Sheets-Shee't 2 f'lverzf or eZZer'Z 5 OliverPatented Sept. 24, 1946 LAPPING METHOD AND MACHINE Delbert S. Oliver,Euclid, Ohio, 'assignor to Pesco Products 00;, Cleveland, Ohio, acorporation of Ohio This invention relates to arrangements for highlyand accurately finishing rotative bearing and sealing surfacesparticularly those having an annularorringshape.

Prior to this invention it has been found extremely difficult toproperly finish a'rad-ially extending bearing and seal surface on'adrive shaft. Equal difiiculty has been encountered'in an effort toaccuratelyfinish the bearing and seal surface on the ring portion ofadiaphragm seal assembly.

I have found that one of the principal reasons for the 'dificultyencountered results from the .diflerences in the relative linearvelocity between the particles of the abrasive and the surface beingfinished. In order to produce a substantially perfectbearin and sealsurface this condition had to be corrected and some; arrangement workedout whereby substantially uniform abrading action could be accomplishedthroughoutthe bearing and seal surface notwithstanding; the fact thatthis surface was-annular or circular in shape. p g 7 It is a principalobject ofthis invention to provide. a finishing arrangement, for annularor ring-shaped bearing surfaces wherein the abrading means is given alinear relative velocity relative to the bearing surface throughout theradial extent thereof that is substantially uniform. 1 I 1 It isafurther object to provide in a finishing arrangement of the present typean improved holding means for the abrading material and holding meansfor the workpiece having abearingsurface thereon to be finished, thework hold ing means being effective to presentthebearingsurface withreference to'the abrading material Application July'31, 1944,. SerialNo. 547,389.

' (i c aim o1i5'1 13i) drawings forming a part thereof and wherein:

Fig. l is a view in elevation indicating schematically an arrangementincorporating a preferred embodiment of my invention; v Fig. 2 is abroken away sectional view substantially on the line '2--2 of Fig.1;

Fig. 3 is a broken away sectional substantially on the line 3+3 of Fig.1.; ,Fig. 4 is a broken away sectional view of an alternative, modifiedembodiment of my invenftionyand I g' w Fig. 5 is a broken away sectionalview taken taken view taken I substantially on the line 5 5 of Fig. l.

Referring now in greater detail to the figures of the drawings and firstto the preferred embodiment shown in Figs. 1 to the arrangement incorporating my invention is composed generally of an abrading or lappingtool assembly A, a-work piece holding assembly 13 adapted to hold a workpiece C in proper relation to the lapping tool, a turning powertransmission assembly indicated generally at D and a source of power E.g

V The present invention is directed particularly to the construction andmode of coaction-of abrading or lapping tool assembly A and work holdingassembly B whereby to provide a more perfect annular or circular sealandbearing surface on work piece C. I v W Abrading or lapping tool assemblyA comprises a base l6 rotatably supporting the finishing tool assemblyfor turning about a vertical axis. A

pair of concentric coaxially v extending radially and support thereforin such a manner that ro tation of-thework holder and of the abradingmaterial .holderin the same direction at selected relativespeedslproduces relativeli-near yelocity of substantially the same orderbetween all of the particles'of the abrasive and the-porticnsof thebearing surfaces-contacted thereby. v

.A further and more detailed object is the pro-,

vision in an arrangement of the present type of a novel and particularlyeffective-holding and tensioning arrangement for abrasive sheetmaterial-suchas emery cloth or sandpaper and functioning to give therequisite backing-support to the sheet when engaged by the bearingsurface to be finished thereby.

Other: and; more detailed obiects, advantages" and uses-of inventionwill become apparent from a reading of the following specification.taken in connection with the accom'panyingv spaced walls or lands II andI2 terminate inra corresponding pair of finishing material supportsingsurfaces I la and Ma, each of these terminal surfaces-being disposedin a plane perpendicular to theaxis of rotation of the finishing toolassembly A. 3 I

The interveningspace between walls l l and I2 is preferably, enlarged toprovide a chamber 13 for the reception of anyenlargement that may bepresent on the work piece C being finished as will appear. The space [4between the finishing material or. abrasive supporting material-surfacesI la and Ilia forms a very important part in the mode of coactionnecessary. to .th e'accom plishment of the substantially perfectbearingand seal surface on the work piece as will appear. To facilitate theintroduction of any enlargement that may be present on the work piece Cthere is providedan enlarged. opening Hi. It will be furtherinctedthatwall terminalsurfaces Ho and l2a each have a radial dimension thatis only a fraction of the total radial dimension of l the Work piece andthatthe bearing seal surface complished by positioning a suitablebonded.

abrasive sheet such as emery cloth or sandpaper in supporting contactwith surfaces I Ia and I2a.

The work holding assembly B preferably comprises a rotatable holdingmember proper I'l formed with a coaxial bore I3 having splines I9protruding radially inwardly from the wall thereof for cooperation withcomplementarily formed splines 21 on the work piece C for effecting the.

driving thereof. The terminal of bore I8 is provided with a resilientcushioning ring 2 I functioning to allow' for the necessary angularadjustments between the holder and the work piece 0 and for holding thesame'firmly but resiliently against the abrading or lapping tool A.

The work piece C may take a number of different forms the essentialstructure of each of which includes an annular or ring shaped bearingand seal surface 26 extending in a radial plane perpendicular to thenormal axis of rotation of the work piece C. The work piece C must bearranged in driving relation to the holder B and in the present instancethis is accomplished by the splines 21 on the work piece cooperatingwith the complementary splines IS on the holder. The particular workpiece C shown in Fig. 3 further includes a reduced cross section coaxialstem 28 terminating in a second enlargement 29 which may also havesplines thereon. The present abrading tool assembly A is particularlyeffective for cooperation with this type of work piece since the reducedcross section stem 28 readily passes between spaced walls II and I2and-the enlarged chamber I3 provides for enlargement 29 carried on theterminal portion of the work piece.

Turning power transmission assembly D may take various forms theessential characteristic required thereof being that abrading or lappingtool assembly A must be rotated in the same direction as work holdingassembly and work piece C. Furthermore the respective turning rate mustbe properly correlated with reference to one another in order toapproximate as near as practicable the ideal abrading conditions. It isdesired that the relative linear velocity between any radial point onthe ring or annular shaped bearing and seal surface 26 and the abradingparticles contacting the same be substantially the same throughout bothfor the inner abrading material supporting surface Na and *the outersurface I2a. It is believed that the present arrangement more nearlyapproximates this ideal condition than any other heretofore available.By the optimum choice of the relative dimensions of surfaces I I a ofthe tool assembly and the bearing seal surface 26 of the work piece andby choosing the optimum relative rate of rotation of the tool assemblyand the work piece the above ideal mode of coaction is approximatelyrealized.

I have found that particularly effective results are obtained by havingthe radii of walls I I and I2 several times as large as the radius ofthe annular surface to be finished. In addition it is important that theradial width of the respective abrasive material supporting surfaces lI! and I2 1 be no greater than the radial width of the surface 26 to befinished and preferably slightly smaller. It is of still furtherimportance that the annular surfaces 25 overlap wall terminal surfaceIla radially inwardly as indicated at 25a and likewise overlap outerterminal wall surface I2a radially outwardly as indicated at 2612. Ihave found that particularly elfective results are obtained if the meanradius rI2 of outer termina; wall surfaces In is made to be of the orderof about six times the value of the mean radius 126 of surface 26 to befinished. By having the mean radius rI I of inner wall surface i Ia andthe mean radius N2 of outer wall surface I2a arranged as described,employing a width of surfaces Ila and I211 not greater than the width ofannular sur face 26 there results an overlapping between the severalsurfaces both radially inwardly and radially outwardly. It will nowappear that when the work piece C is rotated'in the same direction asthe tool assembly A the relative velocity between the outer lapping faceI'Za. and annular surface 26 will be the difference between the linearvelocity of the surface I2a and the linear velocity of the surface 26.The relative velocity between the inner lapping surface Ila and theannular surface 26 will be the sum of the velocity of the inner lappingsurface Na and the velocity of the surface 26. While it will be apparentthat, strictly speaking, this is only true as regards an average takenwith reference to the median radii TI I, M2, and T26, it'is important tonote that for all practical purposes this arrangement and mode ofcoaction produces a substantially perfectly flat surface. In otherwords, by means'of this arrangement it is possible for all practicalpurposes, to compensate for the fact that the outer lapping surface .I2ais moving faster than the inner surface Na and to thus obtain the samerelative velocity between the abrading particles and the work surface 26on both sides of the work piece C. It is found that the lapping-surfacesIla and I2 a remain true for a long period of continuous operation andrequire resurfacing only after several hundred pieces have beenfinished.

For the purpose of applying rotative power to abrading tool assembly Aand work piece holder assembly B, transmission assembly D'is providedwhich may comprise a pulley 3| receiving power from any suitable sourceindicated generally at E as being in the form of a drive belt. Pulley 3|may drive work holder assembly B directly and through means of a secondpulley 32 and belt 33 drives a thirdpulley'34. Through a connectingdrive shaft 36 pulley 34 drives a fourth pulley 3'1 in turnconnected bya belt38 to a pulley 39 directly associated with abrading tool assemblyA. By the proper choice of the respective sizes of the several pulleysthe desired optimum relative speed of rotation can be readily effectedbetween abrading tool assembly A and work piece C. I prefer to turnabrading tool assembly A three revolutions while turning work piece Ctwo revolutions. This has been found to give very satisfactory results.i v Turning now to the alternative modification of my invention shown inFigs. land 5, it will be apparent that the same fundamental features areinvolved, this arrangement being particularly adapted for finishing aradially extending bearing and seal surface of the annular type on awork piece having no protuberance extending axially in the direction ofthe abrading surface thus making it practicable to employ a bonded.abrasi-ve such aszemery clothrorsandpaper. The .abrading tool assembly2A; andi-theg-work holder assembly; 23 are arranged to bezdri-ven in-gasimilar manner totha-t described inv the flrstgmodiflcation, the latterfunctioning to,:hold and .present the workpiece "2C for finishingengagement-with the .abrading sheet forming part of theabrading :00 assmb y. 1 A j c.

The abradingtool assembly 2-A5-compriSeS -concentric coaxiallyextendingwalls-fl ll and-H2 corresponding to walls H and 1250f the firstmodification and terminating :in abrasive sheet material I supportingspaced-apart surfaces 1 Ma and 2e. These surfaces I'I la and, l 12aarelikewise dis:

posed int-a plane perpendicular to the axis f rotation of tool assembly2A. -'Iheradius,tuddth,

.zsupported-sealgzfand bearing :ring.

. The arrange- ;mentshownco'mprises :a seal and bearing ring properl.28.fastened about anopening through the radial inner portionzof aflexible diaphragm support czlzaawlcy means of a fastening: ring l28bthe lowetp ortion of which; cooperates with; flexrelationship.

and other relationships of terminal-wall surfaces illa and 2a withreference to thQfWOl'kaIfiBCG to be finished are determined inaccordance with the same fundamentals described in connece tion with thefirstmodiflcation; .Ilfhe periphery of outer wall surface :I l=2a mergeswith :a beveled surface portion H2b for cooperation with radial terminalportions of. a, sheet of abrasive cloth such as emery cloth or sandpaperin asmanner as will appear. An embracing ring M20 is received abouttheouter periphery; of. wall H2 and is formed with a radiallyinwardly/extendingp'rotuberance 1 12d complementarily formedxon theinner side thereoffor,,cooperation with beveled surfacellZbandeffectiveto firmly engage and apply the requisite-tension to theabrasive cloth I5l by contact with-the peripheral :portion' I52 thereofThis; results in "snug. engagement between the abrasive cloth, -l5l and.terminalrsurfaces I I la and -l l2a,-these Qlatter surfaces func-.tioning as a backing support for the abrasive cloth and rendering thesame effective in the desired critical areas sin-contact with thebearing and seal surface I26 of the work piece 20 being finished.

I Clamping ring formed in ring H20. I

Work holding assembly 2B comprises upstanding rotatable supporting shaft.l H formed with an internal bore l Ila receiving a coilcompressionspring in engagement with the inner terminal thereof, the outer terminalof this spring engag .ible ring I21 1 for effectingthe flexible drivingAs in :the case :of. the modification of'Figu 1, it will be seen thatthe features: of criti'calimportance include the provision of radiallyspaced hacking surfaces J .I la and Him In :the more specific aspects ofthis modification it is. also important that wal l surfaces 1 il la 'and1112a be 1 overlapped-both radially outwardly and radially inwardlyby'theibearing and ring surface 126.

'.:.'I'his..;second modification is=of special value in'connec'tion withfinishing bearing and seal surfaces .on bronze bearing rings,itbeing-quite important thatthe bearing surface bemade sub stantiallyperfectly flat. It-has been found necessary tohold'th'ese surfaces toa'per-l'ectionwithin the limits of two light bands. .'Bronze' or anysoft material has a tendency to charge when being lapped by a looseabrasive. fore desirable that a bonded'abrasive such as emerycloth beused and this modification lends itself especially to the use ofemerycloth. The novel features of the holding assemblyare-of particularadvantage in maintaining the requisite tens'ionof the'emery cloth infirm-engagement with the backing surfaces thus insuring greaterperfection in the finish ofthe bearing and seal surface.

While my invention has been disclosed in echnection with certainspecific embodiments there- 7 H20 is fastened in abrasive cloth engagingposition by means of a'radially extending locking pin |I2e carried bythe wall H2 and cooperating with a bayonet slot H2 opposing said holdercomprising a base rotatable ing the closed end of a work supportingmember or bonnet proper I Ilc. Shaft H1 is provided with coaxial splinescooperating with complementarily formed splines l 11d formed on theinner periphery of Work supporting bonnet l I'Ic for effecting drivingrelation therebetween. Work supporting bonnet 1c is formed on the outerportion thereof with a recessed shoulder for the reception of a flexiblering l2! effective to resiliently and drivingly support the work piece2C. The spring 1b is effective to supply the necessary axial pressurethrough the intervening flexible ring |2| to cause the desired abradingaction on annular bearing and sealed ring surface I25, while at the sametime this flexible ring insures the precise alignment required betweenbearing and seal surface I26 andthe underlying surfaces Illa and HMcarry the abrading sheet in supported relation thereon.

The particular work piece 2C is characterized by the absence of anyaxially extending protuberance that would interfere with the properfunctioning of the abrasive cloth and it may include, by way of example,a flexible diaphragm' on an axis parallel with and spaced from theholder axis; two coaxial parallel walls of substantial height havingconfronting abrasive supporting flanges at their ends and defining arelatively deep chamber the entrance to which is restricted by saidflanges, the stem and head of the work piece being received in saidchamber and entrance thereto; and radially alined recesses in saidflanges effecting the insertion of the work piece head into said chamberthereby to engage the seal flange with the abrasive supporting flangesof the lapping assembly.

- '2. An apparatus for lapping a work piece as defined in claim 1wherein yieldable cushioning means are interposed between the holder andthe seal flange to accommodate angular adjustment between the holder andwork piece. I

3. An apparatus for lapping a work piece having a headed stem and a flatradial seal flange;

It is thereto which is restricted by said flang'es,said flanges beingspaced from each other a distance less than theldiameter of the workpiece head, the stem andhead of the work piece being received in saidchamber and entrance thereto, at least one of said flanges having anasymmetric region adapted to efiect the insertion'of the work piece headinto said chamber thus to engage the seal flange with the abrasivesupporting flanges of the lapping assembly. l

4. An apparatus for lapping a work piece which has a headed stem and anannular seal flange, comprising a rotatable work supporting holder; anda lapping assembly opposing said holder comprising a base rotatable onan axis radially oilset from the axis of said holder; spaced 00110811?tric walls of substantial height upstanding from said base; flanges onsaid walls projecting towards each other into the space between. saidwalls and having abrasive supporting surfaces that oppose oppositeregions of said seal flange, said walls defining an annular chamber theentrance to which is restricted by said wall flanges,

the head and stem of said work piece being reporting the work piece; anda lapping assembly opposing said holder comprising a base rotatable onan axis parallel with and spaced from the holder axis; and two annularparallel walls of substantial height having concentric confrontingflanges which provide abrasive supporting surfaces, said walls-andflanges defining a relatively deep "chamber'the entrance to which isrestricted by said flanges, the distance between the confrontingportions of said flanges being less than the diameter of the work piecehead, the head and stem of the workpiece being received respectively insaid chamber and the entrance thereto, said restricted entrance havingan enlarged region for permitting the introduction of the work pieceheadinto said chamber past said flanges, thus providing for engagementof said seal flange with said abrasive receiving surfaces. 6. Anapparatus for lappinga work piece having a headed stem and aflatradial'seal flange spaced from the head, the seal surface having anannular contour arranged in a plane perpendicular to and concentric Withthe stem axis; said apparatus comprising a rotatable holder supportingthe work piece; and a, lapping assembly opposing said holder comprisingabase rotatable on an axis parallel with andspaced from the holder'axis;means on said base defining a relatively deep annular chamber havingradially spaced overhanging concentrically arranged flange portions theouter surfaces of which are adapted to receive'abrasivematerial, saidflanges extending towards each other in overhanging relation'to theouter portion of said chamber thereby providing a restricted entrance ofless width than the-diameter of the work piece head, the head and stemof the-work piece being received respectively in said chamber and theentrance thereto; said restricted entrance having an enlarged' regionfor permitting the introduction of the work piece head into said chamberpast said flanges, thus providing for engagement of said seal flangewith said abrasive supporting surfaces.

- DELBERT S. OLIVER.

